This invention relates to underrun guards for motor vehicles in which a horizontal beam is fitted to the vehicle to reduce the risk of smaller vehicles being forced beneath the guarded vehicle in a collision.
It has long been recognized in many countries that deaths and injuries can be reduced in road accidents involving road transport vehicles by providing underrun bumpers or guards, especially at the rear of the road transport vehicle. What often happens in a rear end impact collision is that a passenger car runs beneath the rear end of a transport vehicle with the result that the passenger compartment is totally crushed. This gives rise to a much greater risk of serious injuries or death among passengers in the car.
As a result, in many jurisdictions, regulations have been introduced requiring road transport vehicles to fit a protective guard or bumper at least at the rear of the vehicle, to prevent so-called underrun accidents. While a fixed, rigid beam supported from brackets depending from the chassis will meet safety requirements of many countries, a problem with such rigid guards is that in every day use they tend to be damaged or deformed, e.g. by reversing the vehicle into loading bays and loading bay equipment or in collision with loading vehicle such as forklift trucks. Once the guard is damaged, the operator of the transport vehicle is no longer confident that the guard meets the requirement of the relevant legislation in the country in which the vehicle is used.
Also, in the event that damage does occur, the operator may not be confident that the guard meets the specification required unless the complete guard is replaced,
There have also been proposals to employ vehicle underrun guards in which the impact energy arising from a collision is absorbed by hydraulic or pneumatic cylinders, or by a sacrificial, deformable component. A problem with these designs is that, generally, they are too expensive or require constant maintenance to ensure that they meet safety and legislative requirements.